Guar gum-polyacrylamide compositions

ABSTRACT

A MIXTURE OF A RELATIVELY UNDEGRADED GUAR GUM HAVING A VISCOSITY AT A CONCENTRATION OF 1% BY WEIGHT IN WATER OF ABOUT 500 CENTIPOISES OR MORE WITH A POLYACRYLAMIDE HAVING A DEGREE OF POLYMERIZATION BETWEEN ABOUT 12,000 AND ABOUT 250,000 WITH THE WEIGHT RATIO OF GUAR GUM TO POLYACRYLAMIDE RANGING FROM ABOUT 0.5:1 TO ABOUT 50:1 OR HIGHER. A PROCESS FOR FORMING A THICKENING COMPOSITION BY ADMIXING A RELATIVELY UNDEGRADED GUAR GUM HAVING A 1% BY WEIGHT AQUEOUS VISCOSITY OF ABOUT 500 CENTIPOISES OR HIGHER WITH A POLYACRYLAMIDE HAVING A DEGREE OF POLYMERIZATION BETWEEN ABOUT 12,000 AND ABOUT 250,000 AT A WEIGHT RATIO OR GUAR GUM TO POLYACRYLAMIDE RANGING FROM ABOUT 0.5:1 TO ABOUT 50:1 OR HIGHER. A THICKENED AQUEOUS MEDIUM CONTAINING A MIXTURE OF A RELATIVELY UNDEGRADED GUAR GUM HAVING A 1% AQUEOUS VISCOSITY OF ABOUT 500 CENTIPOISES OR HIGHER WITH A POLYACRYLAMIDE HAVING A DEGREE OF POLYMERIZATION BETWEEN ABOUT 12,000 AND 250,000 AT A WEIGHT RATIO OF GUAR GUM TO POLYACRYLAMIDE RANGING FROM ABOUT 0.5:1 TO ABOUT 50:1 OR HIGHER WITH THE MIXTURE BEING PRESENT IN AN AMOUNT WHICH IS EFFECTIVE TO SYNERGISTICALLY INCREASE THE VISCOSITY OF THE AQUEOUS MEDIUM.

United States Patent 3,658,734 GUAR GUM-POLYACRYLAMIDE COMPOSITIONS David J. Pettitt, San Diego, Calif., assignor to Kelco Company, San Diego, Calif. N0 Drawing. Filed Oct. 20, 1970, Ser. No. 82,478 Int. Cl. C08f 45/18 US. Cl. 26017.4 ST 24 Claims ABSTRACT OF THE DISCLOSURE A mixture of a relatively undegraded guar gum having a viscosity at a concentration of 1% by weight in water of about 500 centipoises or more with a polyacrylamide having a degree of polymerization between about 12,000 and about 250,000 with the weight ratio of guar gum to polyacrylamide ranging from about 0.5:1 to about 50:1 or higher. A process for forming a thickening composition by admixing a relatively undegraded guar gum having a 1% by weight aqueous viscosity of about 500 centipoises or higher with a polyacrylamide having a degree of polymerization between about 12,000 and about 250,000 at a weight ratio of guar gum to polyacrylamide ranging from about 0.5 :1 to about 50:1 or higher. A thickened aqueous medium containing a mixture of a relatively undegraded guar gum having a 1% aqueous viscosity of about 500 centipoises or higher with a polyacrylamide having a degree of polymerization between about 12,000 and 250,000 at a weight ratio of guar gum to polyacrylamide ranging from about 0.5:1 to about 50:1 or higher with the mixture being present in an amount which is eifective to synergistically increase the viscosity of the aqueous medium.

This invention relates to a thickening composition which, when added to an aqueous medium, produces a synergistic increase in the viscosity of the medium. More specifically, the invention pertains to a composition which comprises a mixture of a relatively undegraded guar gum with a polyacrylamide, its method of preparation and its use in thickening an aqueous medium.

Both guar gum and polyacrylamide are known materials of commerce. I have found that a mixture of these materials, when added to an aqueous medium, produce a synergistic increase in the viscosity of the medium. This result is quite advantageous since it permits the obtaining of significant viscosities in an aqueous medium while using a lesser quantity of the thickening composition.

The guar gum which is employed in my compositions is relatively undegraded such that it will produce a viscosity at a 1% by weight concentration in an aqueous medium of about 500 centipoises or higher as measured with a Brookfield Viscometer, Model LVF, at a spindle speed of 60 rpm. and a temperature of about 25 C. Preferably, the guar gum which is employed in my compositions has a 1% by weight aqueous viscosity of about 900 centipoises to about 3500 centipoises, as measured with a Broolcfield Viscometer described above.

Polyacrylamide is available as a commercial material in three basic forms which are the neutral, anionic and cationic forms. The basic polymer unit for a neutral polyacrylamide is as follows:

| :0 NH: NH2

in which x represents the average number of the repeating basic units in the polymer chain which is defined as the degree of polymerization (DR) of the polymer. A second form of polyacrylamide is the anionic form which has the basic structure:

Patented Apr. 25, 1972 In the above formula, x again represents the average number of repeating structural units in the polymer chain while X is a monovalent negative ion, such as a chloride, bromide or iodide ion.

Polyacrylamide is available in a variety of molecular weights ranging from as low as 200,000 to as high as about 10 to 15 million. When used in accord with my invention, the polyacrylamide should have a degree of polymerization (D.P.) between about 12,000 to about 250,000, which is represented by x in the above structural Formulas I-III. Any of the three forms of polyacrylamide-neutral, anionic or cationicmay be used in conjunction with guar gum in the practice of my invention.

The weight ratio of guar gum to polyacrylamide in my compositions ranges from about 0.5:1 to about 50:1 or higher. Preferably, the weight ratio of guar gum to polyacrylamide ranges from about 2:1 to about 20:1.

In use, my thickening compositions are added to an aqueous medium with sufficient agitation to dissolve the composition in the aqueous medium. The concentration of my compositions in aqueous medium may be varied depending upon the degree of thickening which is desired. Thus, my compositions may be added in any concentration which is effective to cause thickening and, in general, I have found that concentrations of my compositions ranging from about 0.1% to about 3% by weight of the water in the aqueous composition provide satisfactory thickemng.

Certain of my compositions are somewhat sensitive to variations in the pH of the aqueous medium. For example, I have found that my compositions which contain a relatively undergraded guar gum in conjunction with an anionic polyacrylamide, undergo a marked change in viscosity in an aqueous medium as a result of changes in the pH of the medium. It was found that a mixture of 20 parts by weight of relatively undergraded guar gum having a 1% by weight aqueous viscosity of 1720 cps. with one part by weight of an anionic polyacrylamide having a molecular weight of 10 to 15 million and a 1% by weight aqueous viscosity of 240 centipoises produced a viscosity of 2600 centipoises at a concentration of one percent by weight in distilled water at a pH of 7. At a pH of 5, the viscosity of the aqueous medium was 1850 centipoises and at a pH of 9, the viscosity was 2350 centipoises. The eifect of pH of my compositions which contain a mixture of a relatively undergraded guar gum with either a neutral polyacrylamide or a cationic polyacrylamide was less marked. However, in all cases tested, it was found that my thickening compositions performed best at a pH range between about 5 to about 11.

Tests were also performed to determine the eifect of various acids and salts on the stability of my thickening compositions in an aqueous medium. In these tests, it was found that my thickening compositions were reasonably stable to formic acid, acetic acid, ammonium chloride, and ammonium salts such as benzyldodecyldimethylammonium chloride and benzyltrimethylammonium chloride efiective in improving the dissolving characteristics of the guar gum. That is to say, the mixture of guar gum and polyacrylamide had better dissolving characteristics than guar gum alonei at a 3% by weight concentration for periods ranging up 5 Also, it was found that the presence of the polyacrylto 165 hours. In the tests it was found that phosphoric amide modified the flow properties of a guar gum soluacid at a concentration of 3% by weight caused degradation. This was determined by plotting the solution vistion of my thickening compositions in an aqueous medium cosity of a guar gum solution with respect to the applied to produce a sharp reduction in viscosity. shear rate in reciprocal seconds. These data were obtained To further illustrate my invention, there are presented by use of a Haake Rotovisco Viscometer. By plotting the the following examples in which all parts and percentages solution viscosity on the vertical axis and shear rate on are by weight unless otherwise indicated. the horizontal axis, it was found that the viscosity-shear EXAMPLE I rate curve had an increased negative slope after the addition of the polyacrylamide to the guar gum solution, That Thickening compositions were made p y miXiHg Vary is to say, the addition of polyacrylamide increased the ing quantities of a relatively undegraded guar gum with pseudoplasticity f the guar u solutions. y g quantities of an anionic polyacrylamide having a The pseudoplasticity of the solution refers to the relamoleclllal Weight in the Order Of 10 to 15 million (SePaTaII tionship between the viscosity of the solution and the AP DOW Chemical p y)- he guar gum had a applied shear to the solution. In a p'seudoplastic liquid, Viscosity of 1720 centipoisis at a 1% y Weight cflncemrathe viscosity of the liquid varies in an inverse relation tioll in distilled Water and the p y rylamide had a w'swith respect to the applied shear rate and when the shear cosity of 2240 centipoises at a 1% by weight concentrarate is increased there is an almost instantaneous drop in i n is distilled wat The v s mixtures of guar s the viscosity of the liquid. This property is of great advanwith polyacrylamide were each added to distilled water tage in a number of applications such as, for example, in at a concentration of 1% y weight of h m ture. At a drilling fluid where it is desired that the fluid have a a weight ratio of guar gum to polyacrylamide of 1:1, high viscosity at rest in order to suspend the cuttings and the aqueous medium had a viscosity of 3750 cps.; at a 2:1 a low viscosity under shear such that the fluid can be weight ratio, the viscosity was 3670 cps. and at a 5:1 pumped down the drill pipe to the drill and then returned weight ratio the viscosity was 3400 cps. Using a weight to the mud pit at the surface where the cuttings are ratio of guar to polyacrylamide of 10: 1, the viscosity was removed. 2800 cps. and at a weight ratio of 20:1, the 1% aqueous Also, the property of pseudoplasticity is of great advanviscosity was 2500 cps. tage in a textile print paste which must flow readily dur- As shown by the above data in Example I, my thickening its application to the fabric and must then set up on ing compositions produce a synergistic increase in the visthe fabric so that the applied color does not run. In this cosity of an aqueous medium over a wide range of weight regard, my compositions are admirably suited for use in ratios of guar gum to polyacrylamide. Also, my compOsia textile print paste because of their general stability to tions can be employed over a wide concentration range. various acids and to ammonium salts. It was also found Thus, when Example I is repeated at thickener concentrathat my compositions were generally compatible with tions ranging from 0.1 to 3.0 percent by weight, syncationic dyes with the exception of methylene blue. ergistic thickening of the aqueous medium is obtained. I claims In other tests which were performed, a number of addi- 1. A composition comprising a mixture of guar gum tional thickening compositions of my invention were forand a polyacrylamide with a weight ratio of guar gum to inulated and tested in distilled water to determine their polyacrylamiide of about 0.5 to 1 to about to 1, said effect in increasing the viscosity of an aqueous medium. guar gum having a one percent by weight aqueous vis- These data are presented in the following table: 45 cosity of at least about 500 centipoises as measured with Guar vls- 1% aqueous viseosities in distilled Molecular wt. PAM viscosity cosity (cps) water(cps.) otguar/PAM mixtures at; (PAM) in (cps) (1% in (1 in disvarying weight ratios oiguar to PM Polyacrylamide (PAM) trade name Type of PAM ons distilled water) tilled water) Magnlfloc 835A American Cyanamid 00-. Anionic 10-15 1,600 1, 720 3,200 3,450 3,390 2,880 2,000 Polyfioc 1220 Betz Company .-do 2,000 1,400 3 030 Polyfloc 1230 Betz Company d 2, 150 Separan N P20 Dow hemical 00-- Neutral- 4 360 Separan NP10 Dow Chemical (30.- do.-. 1 315 Polymer 470 Drew Chemical Corp Cationic 5 470 The molecular weights of the various polyacrylamides a Brookfield Viscometer, Model LVF, at r.p.m. and denoted by the tradename Polyfloc were not available 25 C., and said polyacrylamide having a degree of from the manufacturer. However, from the viscosity data 60 polymerization of about 12,000 to about 250,000. for these polymers, it is clear that they have high molecu- 2. The composition of claim 1 wherein the weight ratio lar weights and a degree of polymerization within the of guar gum to polyacrylamide is about 2:1 to about range between about 02,000 and about 250,000. 20:1.

As demonstrated in the table, the 'various compositions '3. The composition of claim 1 wherein said polyacrylof my invention include a considerable range of ratios amide is an anionic polyacrylamide. of guar gum to polyacrylamide and include the use of 4. The composition of claim 1 wherein said polyacrylvarious types of polyacrylamide, including anionic, neuamide is aneutral polyacrylamide. tral and cationic polyacrylamides. In all of these tests, 5. The composition of claim 1 wherein said polyacrylthe use of a mixture of relatively undegraded guar gum amide is a cationic polyacrylamide. and polyacrylamide, both as specified, produced a syner- 6. The composition of claim 1 wherein said guar gum gistic increase in the viscosity of the aqueous medium to has a one percent by weight aqueous viscosity ranging which they were added. from about 900 cps. to about 3500 cps.

In addition to producing a synergistic viscosity increase 7. A method for increasing the viscosity of an aqueous in the aqueous medium, it was found that the addition medium, said method comprising admixing guar gum of the polyacrylamide to guar gum was, in many cases, with a polyacrylamide at a weight ratio of guar gum to polyacrylamide of about 0.5 :1 to about 50:1, said guar gum having a one percent by weight aqueous viscosity of at least about 500 centipoises as measured with a Brookfield Viscometer, Model LVF, at 60 r.p.m. and 25 C., and said polyacrylamide having a degree of polymerization of about 12,000 to about 250,000.

8. The method of claim 7 wherein said polyacrylamide is an anionic polyacrylamide.

9. The method of claim 7 wherein said polyacrylamide is a neutrai polyacrylamide.

10. The method of claim 7 wherein said polyacrylamide is a cationic polyacrylamide.

11. The method of claim 7 wherein said guar gum has a one percent by weight aqueous viscosity ranging from about 900 cps. to about 3500 cps.

12. The method of claim 7 wherein the weight ratio of guar gum to polyacrylamide is about 2:1 to about 20:1.

13. A thickened aqueous medium containing water and a mixture of guar gum and a polyacrylamide in an amount elfective to thicken said medium, the weight ratio of said guar gum to said polyacrylamide ranging from about 0.5 to 1 to about 50 to 1, said guar gum having a one percent by weight aqueous viscosity of at least about 500 centipoises as measured with a Brookfield Viscometer, Model LVF, at '60 r.p.m. and 25 C., and said polyacrylamide having a degree of polymerization of about 12,000. I

14. The composition of claim 13 wherein said polyacrylamide is an anionic polyacrylamide.

15. The composition of claim 13 wherein said polyacrylamide is a neutral polyacrylamide.

16. The composition of claim 13 wherein said polyacrylamide is a cationic polyacrylamide.

17. The composition of claim 13 wherein said guar gum has a one percent by weight aqueous viscosity ranging from about 900 cps. to about 3500 cps.

18. The composition of claim 13 wherein the weight ratio of guar gum to polyacrylamide is about 2:1 to about 20:1.

19. The composition of claim 13 wherein the concentration of said mixture of guar gum and polyacrylamide is about 0.1% to about 3% by weight of the water in said aqueous medium.

20. The composition of claim 18 wherein the concentration of said mixture of guar gum and polyacrylamide is about 0.1% to about 3% by weight of the water in said aqueous medium.

21. The composition of claim 13 having a pH ranging from about 5 to about 11.

22. The composition of claim 14 having a pH ranging from about 5 to about 11.

23. The composition of claim 14 having a pH of about 6 to about 9.

24. The composition of claim 14 having a pH of about 7.

References Cited UNITED STATES PATENTS 2,758,102 8/1956 Grummitt et al. 2'60-29.6 3,346,555 10/1967 Nordgren 260-209 3,511,791 5/ 1970 Puetzer et al. 260-17.4

WILLIAM H. SHORT, Primary Examiner L. L. LEE, Assistant Examiner US. Cl. X.R.

26029.6 HN, 29.6 'PT 

